1. Technical Field
The present invention relates to a guided travel control device for an unmanned vehicle, and more particularly to a device for guiding and moving an unmanned vehicle along a target travel course at a target speed without generating a guidance error between the target travel course and the current position of the unmanned vehicle.
2. Related Art
In a wide working site, such as a rock-crushing site or mine, sediment transport is carried out by driving an unmanned vehicle such as an unmanned dump truck. As shown in FIG. 1, an unmanned vehicle 10 is guided and moved along a target travel course 70 at target speed V by feeding back a guidance error ΔP between a target position Q on the target travel course 70 and the current position P of the unmanned vehicle 10 so that this guidance error ΔP becomes zero. The unmanned vehicle 10 is guided and moved by automatically controlling a steering mechanism and a traveling mechanism.
The wide working site usually has a rough landscape. A travel passage width 80 in which the unmanned vehicle 10 can travel narrows or broadens depending on the area in the wide working site. The area outside a borderline 81 of the travel passage width 80 is a shoulder, cliff, oncoming lane or the like where the unmanned vehicle 10 cannot travel.
When the unmanned vehicle 10 is subjected to guided travel control, a control error occurs, or another error occurs due to skid of the wheels. For this reason, it is inevitable that the guidance error ΔP occurs.
It is generally known that the guidance error ΔP tends to increase as the target speed V and the guiding speed of the unmanned vehicle 10 are increased. For this reason, the target speed V cannot be accelerated to a speed at which the unmanned vehicle 10 could stray from the travel passage width 80.
Therefore, conventionally, the target speed V was set based on the location where the travel passage width 80 is the narrowest on the travel path where the unmanned vehicle 10 travels. Specifically, low target speed V was set at which the unmanned vehicle 10 would not stray from the narrowest travel passage width 80.
Also, a guidable width 90 was set according to the narrowest travel passage width 80. The unmanned vehicle 10 was subjected to the guided travel control within the width of this guidable width 90.
When the guidance error ΔP between the target position Q on the target travel course 70 and the current position P of the unmanned vehicle 10 exceeds a certain level, and the unmanned vehicle 10 approaches a borderline 91 of the guidable width 90 while being guided and caused to travel within the guidable width 90, speed control is carried out such as to reduce the speed of the unmanned vehicle 10 or to stop the unmanned vehicle 10. As a result, the unmanned vehicle 10 is prevented from straying from the guidable width 90 and approaching the borderline 81 of the travel passage width 80.
There has been a demand for increasing the speed of guiding the unmanned vehicle and improving the efficiency of sediment transport in the wide working site.